The intensity of moonlight varies greatly depending on its phase, but even the full Moon typically provides only about 0.05–0.1 lux illumination. When the Moon is at perigee and viewed around upper culmination from the tropics, the illuminance can reach 0.32 lux. The full Moon is only about one-millionth as bright as the Sun.
The color of moonlight, particularly around full moon, appears bluish to the human eye compared to most artificial light sources due to the Purkinje effect. Moonlight is not actually tinted blue, and although moonlight is often referred to as "silvery", it has no inherent silvery quality. The Moon's albedo is 0.136, meaning only 13.6% of incident sunlight is reflected from the Moon. Moonlight generally hampers astronomical viewing, so astronomers usually avoid observing sessions around full Moon. It takes approximately 1.26 seconds for moonlight to reach Earth's surface.
In folklore, moonlight sometimes has a harmful influence. For example, sleeping in the light of a full Moon on certain nights was said to transform a person into a werewolf. The light of the Moon was thought to worsen the symptoms of lunatics, and to sleep in moonlight could make one blind, or mad. Nyctalopia (night blindness caused by a lack of vitamin A) was thought to be caused by sleeping in moonlight in the tropics.
"Moon blindness" is a name for equine recurrent uveitis. Moonlight is no longer thought of as the cause.